1. Field of the Invention
The present invention relates to a backlight system, and more particularly, to a backlight system having a light guide plate configured for diffusing light beams.
2. Description of the Prior Art
A liquid crystal display is capable of displaying a clear and sharp image through millions of pixels of image elements. It has thus been applied to various equipment in which a message or picture needs to be displayed, such as mobile phones and notebook computers. However, liquid crystal in the liquid crystal display does not itself emit light. Instead, the liquid crystal has to be lit up by a light source so as to clearly and sharply display text, pictures and images.
A conventional backlight system generally comprises a plurality of elements, such as a light source, a reflective plate, a light guide plate, a diffusion plate, and a prism layer. Among these elements, it is generally believed that the light guide plate is the crucial element that plays a vital role in determining the performance of the backlight system. The light guide plate serves as an instrument for receiving light beams from the light source, and for evenly distributing the light beams over the entire light guide plate through reflection and diffusion. In order to keep light evenly distributed over an entire surface of an associated liquid crystal display, the diffusion plate is arranged at a side of the light guide plate.
Taiwan Patent Publication No. 486101 issued on May 1, 2002 discloses a backlight system, which is represented in FIG. 8. The backlight system 100 generally comprises a prism layer 130, a diffusion plate 120, a light guide plate 110, and a linear light source 140. The linear light source 140 is arranged at a side of the light guide plate 110. The prism layer 130 comprises first and second prism plates 131, 133. Light beams from the light source 140 are directed to emit from a surface of the diffusion plate 120 via the light guide plate 110. The emitted light beams eventually penetrate the prism layer 130.
The light guide plate 110 further includes a reflective layer 150 disposed thereon by means of sputtering.
The backlight system 100 is provided with the diffusion plate 120 so that the light beams are evenly distributed and can provide uniform luminance. However, the diffusion plate 120 is an extra element that adds to costs of raw materials and costs of manufacturing. In addition, when the light beams travel from the light guide plate 110 and from the diffusion plate 120, they must cross two interfaces. Each interface has two media with different reflective indices. Portions of the light beams are reflected and absorbed, and the luminance of the backlight system 100 is reduced accordingly. As a result, optical performance of the backlight system 100 is diminished.